1. Field of the Invention
The present invention relates to a head suspension for a disk drive installed in an information processing apparatus such as a personal computer, and a method of manufacturing the head suspension.
2. Description of the Related Art
A hard disk drive (HDD) records and reproduces information to and from rotating magnetic or magneto-optical disks. The disks are supported with a carriage that is turned around a spindle by a positioning motor.
An example of the carriage is disclosed in U.S. Pat. No. 4,167,765. The carriage of this disclosure includes a carriage arm, a head suspension attached to a front end of the carriage arm, a head attached to the head suspension, and a slider attached to the head. The slider faces a disk. When the disk is rotated at high speed, the slider slightly floats from the disk, and an air bearing is formed between the disk and the slider.
The head suspension includes a load beam made of a precision thin plate spring, a flexure made of a very thin plate spring fixed to a front end of the load beam by, for example, laser welding, and a base plate fixed to a base of the load beam by, for example, laser welding. The base plate is attached to a suspension attaching face of the carriage arm.
Recent hard disk drives employ high-density disks and drive the disks at high speed. Such high-density disks involve narrow tracks, and therefore, disturbances due to, for example, airflow and disk fluttering result in moving the head away from a track center.
It is important to control such disturbances and increase controllable bands, to maintain the head on a track center.
It is also important to control the amplitudes and frequencies of various resonance modes and air disturbances concerning the head suspensions and carriage arms between the actuator and the sliders in the disk drive. The recent high-density, high-speed disks require head suspensions of high rigidity and low spring constant.
FIG. 1 shows a head suspension 201 for a disk drive according to a related art. The head suspension 201 has a load beam 203 consisting of a rigid part 203a of L1 in length and a resilient part 203b of L2 in length. The rigid part 203a and resilient part 203b are integrally formed from a single metal plate. It is difficult, therefore, to simultaneously satisfy high rigidity for the rigid part 203a and a low spring constant for the resilient part 203b. 
The rigid part 203a improves torsional rigidity if it is thickened. This, however, increases the weight of the rigid part 203a. The material and thickness of the rigid part 203a are restricted by those of the resilient part 203b. Namely, it is impossible to thicken the rigid part 203a separately from the resilient part 203b. 
FIGS. 2 and 3 show a head suspension disclosed in U.S. Pat. No. 5,187,625. The head suspension 201A has a rigid part 203a and a resilient part 203b and is supported by a carriage arm through a base plate 209. Parts corresponding to those of FIG. 1 are represented with like reference numerals.
FIG. 3 is a sectional view taken along a line SC—SC of FIG. 2. A load beam 203 of the head suspension 201A has a three-layer structure. Namely, the load beam 203 consists of two metal plates 217 and 219 and a resin layer 221 interposed between the metal plates 217 and 219, to damp various resonance modes of the head suspension 201A.
In the head suspension 201A, the resilient part 203b has also a three-layer cross section like the rigid part 203a, and therefore, it is difficult to provide a low spring constant and correctly apply spring load.
The head suspension 201A has a channel 205 formed by bending the three-layer structure. Bending such a multilayer structure is difficult to correctly achieve and increases cost.